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Check Engine Light On? What It Means and What to Do

The check engine light can mean anything from a loose gas cap to a misfire that's damaging your catalytic converter. Here's how to tell.

By NewGen Auto Repair, Santa Ana · Updated October 22, 2026

Steady light

Something isn't right, but it's not an emergency. Get the car scanned soon. Common causes:

  • Loose or damaged gas cap
  • Oxygen sensor
  • Evaporative emissions (EVAP) leak
  • Mass airflow sensor
  • Catalytic converter efficiency

Flashing light

A flashing light usually means an active misfire. Unburned fuel can overheat and ruin the catalytic converter. Reduce speed and get the car checked right away.

Smog check

In California, a car with the check engine light on will fail a smog check. Fix the cause first, then drive normally for a while before testing so the readiness monitors complete.

The first step: a scan

A code tells us where to look, not always what to replace. At NewGen Auto Repair the computer diagnostic scan is free**: we read the codes, explain them and give you a written estimate before any paid testing or repair.

FAQ

Can I drive with the check engine light on?

If it's steady and the car drives normally, usually yes for a short time — get it scanned soon. If it's flashing, reduce driving and get it checked right away.

Will disconnecting the battery fix the check engine light?

It may turn the light off temporarily, but it also erases data needed for diagnosis and smog readiness. The problem will come back.

This article is general information, not legal or insurance advice. Rules and policies change — check your policy and the official source, or ask us.

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*Deductible assistance of up to $1,000 is available only on insurance claims where your insurance company has approved a repair amount of $8,000 or more and the repair is performed in accordance with that insurer-approved estimate (California Penal Code § 551(b)). We never increase a repair estimate to cover a deductible. Not available on customer-pay repairs. Ask us for details before your repair begins.

**Free computer diagnostic scan: we read and explain your vehicle's trouble codes at no charge, no purchase required. If the problem needs in-depth testing (labor), we give you a written estimate and get your approval before any paid work, as California law requires.

†Warranty: limited lifetime warranty on our collision, body and paint workmanship for as long as you own the vehicle; 24 months / 24,000 miles (whichever comes first) on mechanical repairs, parts and labor. Not covered: normal wear, new damage, abuse or neglect, rust or chips from road debris, and customer-supplied parts. Warranty terms are written on your invoice.

‡Accident towing: you pay nothing out of pocket when you have collision coverage or the other driver is at fault — we pay the tow and bill the insurance company. If no insurance covers the tow, we tell you the price before the truck is sent.

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